Interesting news in the world of firearms (if you follow that kind of stuff). True Velocity’s 6.8x51mm polymer case turns out to work quite well with legacy firearms (machine guns and SAWs), simply by switching the barrel. For those unfamiliar, the 7.62x51mm (which is the NATO dimensions) has the same length as the new 6.8mm, so they fit the chambers quite nicely. https://www.tactical-life.com/news/us-army-6-8mm-weapon-systems/
Not saying I called it, but does anyone remember the caliber used in the Militia issue rifle on Hayek? Hint, hint: 6.8mm, but longer than the 6.8SPC.
James S. Peet, Author, novelist, and all around good guy! 
6.5 Grendel?
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Nope – better. Look at the characteristics – 6.8x51mm vs. 6.5x39mm. The 6.5 could fit the M-4 platform, but not the LMG or SAW platforms that utilized 7.62×51. While the 6.5 outperforms the 5.56 for distance, I don’t believe it’ll outperform the 6.8 (which also utilizes a polymer case which is a lot lighter than brass).
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Are you talking about the 6.8spc? or is this a new cartridge base on the 51mm 7.62 nato necked down to .270 (6.8)?
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Not the 6.8 SPC – the new round is likely a necked down 7.62 x 51 (as the length is identical). The 6.8 SPC was designed to fit into the M4 platform due to it’s better distance performance out of the short barrel. The 6.8x51mm is more designed for larger systems (think M60 for those of us that old).
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270 was the caliber ordnance wanted when the Garland was developed but MacArthur insisted on 30 cal!
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As I recall, that was mainly because the US had a plethora of .30-06 ammo left over from WW I. I believe there are a couple of things that might have saved the US a lot of time & money was to reduce the caliber of the M1, reduce the size, and make it with a detachable box magazine (in other words, similar to the M-14, but with an even smaller round – sort of like what I came up with in Openings.
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